Fiber-to-the-home (FTTH) is the delivery of a communication signal through optical fiber from a central office (CD) or optical line terminal (OLT) to a home or a business of a user. Referring to FIGS. 1A and 1B, today's FTTH systems are mostly offered through point-to-multi-point time division multiplexed (TDM) passive optical networks 100 (PONs) using a passive optical power splitter 122 at a remote node 120 (RN) in the field to share a common transceiver 30 at the CO 20, or through point-to-point (pt-2-pt) optical Ethernets (not shown), where a home-run fiber extends all the way back to a CO and each one is terminated by a separate transceiver as opposed to the shared transceiver 30 as shown. A PON 100 is a point-to-multipoint network architecture is that uses optical power splitters 122 to enable a single optical feed fiber 10 to serve multiple users 150a-150n (e.g. 16-128). PON 100 provides optical signals from a CO 20 and includes an optical transmitter/receiver or transceiver 30 to a number of optical network terminals (ONUs) 150 that each includes a bidirectional optical transceiver.
Referring to FIG. 1B, one feeder fiber 10 is employed from the CO 20 to a remote node 122, where the signal is split and distributed to, for example, 32 optical network units 150aa-150ag. Referring to FIG. 1C, to achieve the same result as the 1:32 power splitter 122a used, in some examples, two 1:16 power splitters 122b are used. However, by substituting the 1:32 splitter 122a with the two 1:16 power splitters 122b, two feeder fibers 10a, 10b are needed instead of the one feeder fiber 10 in the previous examples.
Compared to pt-2-pt home run systems, a TDM-PON provides beneficial savings in the number of feeder fibers 10 (between a remote node 120 and the central office 20, and in the number of optical transceivers 30 at the CO 20 while saving patch panel space to terminate fibers. However, TDM-PON does not scale well with bandwidth growth. The bandwidth per household is often oversubscribed since the bandwidth per optical line terminal transceiver at the central office 20 is shared among all ONUs 150 that are connected to an OLT 30.
Pt-2-pt systems provide the ultimate high bandwidth to end users 152; however, pt-2-pt uses a great number of both trunk fibers 10 and optical transceivers 30. Thus, pt-2pt systems do not scale well with OLT 30 at the central office 20 and the fiber count between CO 20 and the RN 120, resulting in greater space requirements, higher power, and an increased cost.
A properly implemented WDM-PON system provides CO 20 fiber termination consolidation that a TDM-PON system offers, bandwidth scalability similar to pt-2-pt home-run fiber systems and the easy-to-understand end-to-end Ethernet transparency. However, WDM-PON systems are still under development and to satisfy the short-term surge in bandwidth demand, carriers are deploying cost-effective TDM-PON systems which have matured in technology. A non-disruptive migration strategy from TDM-PON to WDM-PON systems is therefore important.
WDM-PON offers every broadband subscriber 152 a separate wavelength. It provides the benefits of both TDM-PON and pt-2-pt architectures. However, traditional WDM-PON systems are incompatible with TDM-PON systems. A WDM-PON network uses a wavelength demultiplexer as opposed to the power splitter used in TDM-PONs in the field to distribute optical signals to end-users.